1. Field of the Invention
The present invention relates to a linear guide apparatus including a guide rail and a slider movable on the guide rail through the rolling of balls and, in particular, to the shape of the ball rolling grooves of a linear guide apparatus.
2. Description of the Prior Art
A prior art linear guide apparatus includes, as shown in FIGS. 7 and 8, a guide rail 1 having axially extending ball rolling grooves 3 formed in both side surfaces and a slider 2 movably straddling the guide rail 1 and having ball rolling grooves 4 respectively opposing the ball rolling grooves 3 of the guide rail 1 formed in inner surface of the slider 2. The slider 2 travels axially on the guide rail 1 through the rolling of balls B to thereby carry a member attached to the slider 2.
However, in the prior art linear guide apparatus, in each of the ball rolling grooves 3 and 4, flank faces F near the side edges of the groove are respectively connected to boundary ridge portions between the flank faces F and the land faces R of both groove banks through chamfered faces C having a slant angle of 45 degrees.
As a result, since the boundary ridge portion is formed with an angle edge, the following problems are encountered.
In the case where a moment load is applied to the slider 2 in a rolling direction, pinching or prying results between the guide rail 1 and the slider 2 and, when the balls B are held at the angle edge, the stress is concentrated and the contact surface pressure is locally increased (edge load). Thus, abnormal wear is caused and fatigue peeling is apt to result due to repeated stress.
Further, at the time of assembling the linear guide apparatus, the balls B hit the angle edge causing scratches on the balls B.